Hillary Clinton's capture of the biggest prize of the night - California - gives her an important boost against Barack Obama in the hunt for delegates.

With California in her column, Clinton can now claim coast-to-coast victories from her adopted home state of New York through Tennessee and Oklahoma to Arizona.

That falls short of Barack Obama's tally of states. He won 12 of the 22 that went to the polls yesterday against eight for Clinton. But it was enough for Clinton to claim victory in a speech to supporters last night.

"Tonight we are hearing the voices of people across America - people of all ages, of all colours, of all faiths, of all walks of life," she said.

Obama, in his speech, also claimed victory but he zeroed in on Clinton's weaknesses - her support for the Iraq war and her ties to corporate lobbyists - telegraphing the battles that lie ahead.

Clinton's wins in delegate-rich states such as California and New York could give her an advantage in reaching the magical figure of 2,025 which will determine which candidate wins the Democratic nomination. But she will have to share that haul with Obama.

Even so, it was shaping up to be a good night for Clinton. As expected, she won her home state of New York as well as its backyard, New Jersey. There was vindication as well in her victory in Massachusetts. The win took a huge last-minute infusion of advertising in the state after Ted Kennedy endorsed Obama.

The early win in Massachusetts was important for Clinton who needed some upsets tonight to turn back Obama's momentum and restore her chances of capturing the Democratic nomination in the week ahead. Obama soon posted some good news of his own, chalking up victories audaciously close to Clinton's home terrain - Connecticut and Delaware.

Obama also fulfilled expectations that his grassroots organisations would pay dividends across the midwest and in caucus states. He easily won in Colorado, Kansas, Minnesota and North Dakota.

But by the time polls closed in California, the larger point had been made: the momentum that Obama had been riding for the last week may have turned.

Clinton's strong showing after a week which seemed to belong to Obama now give her a head start in the battle of perceptions that lies ahead.

In part, her wins represent a humbling moment for Ted Kennedy. He had thrown his clan's prestige behind Obama, practically annointing him the rightful heir to his brother. He campaigned vigorously with Obama in California and Arizona. But in the end those two states went to Clinton - as well as Kennedy's home state of Massachusetts.

The result establishes Clinton as a successful campaigner in her own right. Unlike in South Carolina, where her husband led a nasty and divisive campaign against Obama, she was centre stage in the battle for Super Tuesday. Bill Clinton, though he hit the campaign trail, steered clear of controversy.

The final outcome from last night's contests could take several days to emerge. In part, that is due to the Democratic party rules which award delegates proportionally in every state. That could benefit second-place finishers, who would otherwise be eliminated under a winner-takes-all system.

Early voting in several states, including California, also could delay a result.

The contest in the coming weeks now depends on the ability of both camps to persuade voters and pundits that they performed better than expected.

In reality, however, the two contenders fell back on their core supporters.

Clinton, as in previous contests, relied heavily on support from white women as well as pensioners. She also dominated the Latino vote, winning 75% of their votes in her home state of New York.

But Clinton showed real weakness in her ability to compete against Obama for male votes. Obama won majority of the male vote everywhere except New York and Tennessee. He also dominated the African-American vote - even among African-American women - winning 90% of the black vote in New Jersey. Obama also improved his share of the white vote. He won 39% of the white vote in Georgia, and close to half of the white vote in California.

Those strengths help maintain him as the favourite as the campaign moves into three back-to-back contests over the next week.

Obama is expected to do well in Louisiana, which holds its caucus on Saturday, because of the large African-American population. Obama is also well placed for the contests in Washington, DC, and neighbouring Maryland and Virginia next week.

A string of wins from Washington state through Louisiana and Washington, DC, could give him an insurmountable advantage - especially if he is able to rebuild his momentum. Candidates need to win over 2,025 delegates to secure the Democratic nomination.

The Clinton campaign has pinned its hopes on March 4, when the powerhouse states of Ohio and Texas, go to the polls. Clinton has been endorsed by the popular governor of Ohio, Ted Strickland. Her economic message is also expected to resonate in a state that has been hurt by job losses. She is also counting on a strong showing in Texas, which has a large Latino population, to put her over the top and secure the nomination.